All LEAF variants are designed to run on small, embedded systems which do not provide a suitable platform for software development. The distribution therefore needs to be prepared on a separate "build" system and installed onto the "target" system.
The build system needs to run Linux but it can be any modern distribution which includes the pre-requisites described on the next page.

One enhancement from Bering-uClibc 4.x is that the build environment can have different architecture that target arch, because true cross-compilation is used.